This invention relates to photo-therapy or low level light therapy (LLLT) used is to stimulate natural healing functions. More particularly, the present invention relates to a new and improved method and device for delivering therapeutic light energy, preferably non-coherent infrared light, which makes use of relatively inexpensive light emitters that are controlled to increase the amount of light energy absorbed by the tissue while still increasing the useable longevity of the emitters under a variety of different portable and use conditions.
Photo-therapy is the application of light energy to biological tissue for the purpose of stimulating certain biological functions, such as natural tissue healing and regrowth processes. Alternatively, a higher power level of photo-therapy may inhibit natural biological functions of the tissue or destroy the tissue, as may be applied in the case of cancerous tissue.
The exact nature of the benefits or effects of photo-therapy on the tissue are not known with certainty. However, many studies have shown that a low level of light and/or heat radiation on tissue is associated with enhanced tissue healing.
Therapists have used photo-therapy to treat a variety of illnesses, injuries and conditions. For example, photo-therapy has been used to treat soft tissue injuries such as capsulitis, bursitis, sprains, strains, hematomas and tendinitis; acute and chronic joint problems such as osteoarthritis, rheumatoid arthritis, and ligament and tendon injuries; chronic pain such as post herpetic neuralgia, chronic back and neck pain, metatarsalgia, trigeminal neuralgia, brachial neuralgia, plantar fisciitis, frozen shoulder and carpal tunnel syndrome. Photo-therapy has also been used to treat non-union and small bone fractures, among other things. Photo-therapy has been used to treat herpes, apthous ulcers, leg ulcers, dermatitis, wound healing, burns, acute epididymitis, otorhinolargngology, gynecology, obstetrics, superficial AP stimulation and tonification, cosmetic imperfections and acne, among other things.
Generally, photo-therapy is accomplished by radiating light energy into a patient""s tissue at or below the skin or surface of the tissue. The radiation is applied at wavelengths either in the visible range or the invisible infrared (IR) range by placing the light source in close proximity to, even touching, the patient""s skin. Photo-therapy may also be accomplished by applying coherent and non-coherent light energy, lased and non-lased light energy, and narrow and broadband light energy, in either a continuous or pulsed manner. The radiation energy is also typically applied at a low power intensity, typically measured in milliwatts. The relatively low radiation energy applied in therapy is called low level light therapy (LLLT).
Visible light radiation typically provides therapeutic effects at the surface of the tissue, i.e. at the skin. IR radiation has a wavelength that penetrates through the skin to achieve deeper therapeutic effects on subcutaneous and deeper tissue. The depth of the therapeutic effect has to do with the absorptivity of the tissue to which the radiation is applied. Deep tissue include substantial water but the skin is relatively dry. The absorptivity characteristic of water peaks at radiation wavelengths of about 900 nm. IR radiation in range of wavelengths from 760-1260 nms penetrates into the deeper sub-dermal tissue. Deeper tissue treatment is useful for healing musculoskeletal injuries, for sports therapy, for reaching deeper acupuncture and myofascial trigger points, and for healing deep wounds, among other things.
Since 900 nm wavelength radiation achieves maximum penetration into most tissue, it is advantageous to supply IR radiation at or near a 900 nm wavelength. Light sources that emit radiation near a 900 nm wavelength are lasers, and lasers are expensive and/or difficult to operate. Examples of radiation emitting sources operative at a 900 nm wavelength include helium neon (HeNe) lasers, alexandrite, titanium sapphire, chromium doped fluoride lasers, and semiconductor diode lasers. The relatively high expense of these types of lasers makes it economically feasible to incorporate only a single one, or a few, of such radiation sources in a photo-therapeutic device. With the reduced number of light emitting sources, the effective treatment area may become substantially limited to a relatively small area.
Other types of radiation light sources such as conventional non-coherent IR light emitting diodes (LEDs) may be employed, but the radiation emitted from such devices typically falls well outside of the peak absorptivity range for water. Using such light source devices achieves less-than-optimal energy penetration and absorption within the tissue. Gallium aluminum arsenide (GaAlAs) LEDs have a room temperature radiation wavelength of approximately 880 nm. Even though this radiation wavelength is closer to the 900 nm peak absorptivity wavelength for water, it is still not optimum for maximum energy absorption. Furthermore, GaAlAs LEDs are more expensive than other types of non-coherent IR LEDs, thus adding a cost consideration to the overall price of the photo-therapy device. In addition, non-coherent IR LEDs are prone to burn out after prolonged periods of continuous use.
One approach to avoiding premature failure resulting from long time periods of continuous use of non-coherent IR LEDs in photo-therapy devices is to pulse the IR LEDs on and off. Pulsing at a predetermined duty cycle adds to the useful longevity of the device because it is only energized on a part-time basis. Pulsing increases the useful life of the device, thereby somewhat offsetting the high cost of the light emitting devices.
One problem with pulsing the photo-radiation sources, particularly a large array of IR LED sources, is that the entire array is turned on and off at the same time, causing substantially large changes in the amount of current conducted by the IR LED sources during the on time period compared to the time periods when the LED sources are nonconductive. The circuit elements necessary to create and sustain such current differentials are themselves large and expensive.
The current conducted by the IR LED sources causes them to heat. The wavelength of the IR radiation emitted is related to the temperature of the LEDs. If the temperature of the LEDs can be controlled, the operating wavelength of energy emitted can be controlled. More precisely controlling the wavelength of the emitted energy can enhance the effectiveness of the treatment. However, thermal instability of many IR sources makes it difficult or impossible to control the effectiveness of the wavelength of the emitted radiation.
Another disadvantage of many photo-therapy devices is the inability of the devices to operate on a wide range of voltage inputs. This restriction prevents photo-therapy and LLLT devices from being portable and convenient to use, since they must generally be connected to a conventional commercial AC mains power supply. This power supply restriction effectively limits the photo-therapy and LLLT devices for use only at home or in a treatment facility, where a ready source of AC power is available. Thus, most existing photo-therapy or LLLT devices cannot be used in a vehicle to provide treatment for chronic pain when sitting and driving for long periods, or on a sports field to provide immediate treatment for sporting injuries, or by an emergency medical team to provide early treatment to accident victims.
Photo-therapy is sometimes applied conjunctively with heat therapy. A heat source in the photo-therapy device will transfer heat to the surface of the tissue. For deep tissue treatment, surface heating is entirely impractical, since the surface tissue would have to be heated to intolerable temperatures to effectively penetrate to the deeper tissue. The deep penetrating IR wavelengths are preferable for use in deep tissue treatment.
It is with respect to these and other considerations, that the present invention has evolved.
One aspect of the invention involves a photo-therapy or LLLT device which utilizes relatively low-cost IR LEDs, such as a gallium aluminum arsenide LEDs, which are controlled to cause them to emit radiation at a wavelength which is closer to the 900 nm peak absorptivity characteristic of water. As a result, less expensive radiation emitting sources may be employed to obtain energy penetration benefits comparable to those obtained from considerably more expensive laser sources.
To achieve these and other similar improvements, a photo-therapy device of the present invention includes an emitter, such as an infrared light emitting diode, which emits infrared radiation at a photo-therapeutic wavelength when current is conducted through the emitter. The wavelength of the infrared radiation is related to the temperature of the emitter, and the temperature of the emitter is related to the current conducted through the emitter. A temperature regulation circuit of the device includes a temperature sensor disposed proximate to the emitter to sense the temperature of the emitter. A temperature regulation circuit supplies a control signal related to the temperature of the emitter sensed by the temperature sensor. A controllable power supply is connected to the emitter and responds to the control signal to supply current to the emitter to establish and maintain a predetermined temperature of the emitter to result in the emission of infrared radiation at a predetermined wavelength. In this manner, the wavelength of the emitted radiation is controlled to establish the desired emitted radiation wavelength during the course of the photo-therapy which is closer to the wavelength for optimal energy absorption from the light energy.
Another aspect of the present invention involves pulsing the light emitters to prolong their useful lifetime without creating unacceptable and difficult-to-handle current fluctuations, all of which contributes to simplifying and reducing the cost of the photo-therapy or LLLT device. To achieve these and other improvements, the photo-therapy device includes a plurality of emitters arranged in an array, with the array having groups of at least one emitter per group. One controllable switch is associated with each group, and the controllable switch conducts current through each emitter of the associated group. A selector is connected to each of the controllable switches, and the selector supplies an activation signal to each of the controllable switches to cause each of the controllable switches to become conductive. Each row of emitters as an LED that emits light in the visible spectrum, and thereby serves as an indicator to the user that each row of emitters is working properly. A controllable power supply is connected to the emitters of the array, and it applies a controllable level of output voltage to the array. The level of the output voltage establishes the amount of current flowing through the emitters.
Another aspect of the present invention involves a photo-therapy or LLLT device which is portable and capable of supplying photo-therapy in a variety of different locations and situations other than exclusively at home, in the practitioner""s office or in treatment facilities. As well, the radiation may be applied in more convenient conditions, such as while traveling, more quickly following an accidental injury, or while transporting an accident victim to an emergency care facility. To accomplish these and other similar improvements, a boost type switching power, or voltage, supply is included within the photo-therapy device. The power supply applies a voltage to the radiation emitters. The boost type switching power supply includes an inductor electrically connected at one terminal to an input voltage supply, a filter capacitor connected at an other terminal of the inductor, a controllable switch connected at the other terminal of the inductor to conduct current through the inductor from the input voltage supply, and a switching regulator connected to the controllable switch. The switching regulator controls a conduction time and a non-conduction time of the controllable switch in response to the output voltage and the current conducted through the inductor. The amount of output voltage from the boost type power supply is directly related to the conduction time of the controllable switch, relative to the non-conduction time of the controllable switch. Adequate power for the photo-therapy devices thereby derived from a wide range of input voltages because of the functionality of the boost-type power supply.
Other uniquely beneficial aspects of the present invention relate to the application of photo-therapeutic infrared radiation to enhance the natural healing process of tissue which has been bitten by insects such as mosquitoes, and gum tissue and to relieve the pain created by headaches.
A more complete appreciation of the present invention and its scope, and the manner in which it achieves the above noted improvements, can be obtained by reference to the following detailed description of presently preferred embodiments of the invention taken in connection with the accompanying drawings, which are briefly summarized below, and the appended claims.